The invention relates to a method and to an apparatus for monitoring and controlling the course of reaction during the refining of crude iron, the reaction being caused to occur by blowing oxygen or oxygen-containing gas onto a molten crude iron bath in a converter.
In oxidation refining processes the formation of slag constitutes one of the essential criteria of the blast process. The guidance of the lance and the supplying of the oxygen have a considerable influence on the formation of the slag.
According to the present state of the art, the operator of the blast furnace determines the growth of the layer of slag and controls the feeding of the melt mainly in dependance upon the sound level. The measurement of the sound level involves the measurement of the intensity of the noise of the blast (the discharge of O.sub.2 from the discharge nozzle) as a function of time. At the start of the blast operation, the lance is moved a distance of for example 2.80 meters from the quiescent bath, and the noise intensity curve displays a high noise level. As emulsion forms, the height of the slag layer increases. During this time the lance is lowered. When the discharge nozzle of the lance dips into the slag, the noise of the blast becomes noticeably attenuated. At this moment, the height of the slag layer in the converter can be readily determined from a knowledge of the height at which the discharge end of the lance is located. During the further course of the reaction, the lance is further lowered and the slag layer continues to rise; in the extreme case, the slag can even run out through the mouth of the converter. Information concerning the exact height of the slag layer in the converter, after the slag layer has risen above the discharge nozzle of the lance, is no longer available. Upon termination of the blast operation, the slag collapses. However, the lance is at its lowermost position, and since the slag layer despite its collapse will still be above the discharge nozzle of the lance, the noise intensity curve will not show a marked change at this time.
The measurement of the noise intensity is unquestionably a useful expedient for the operator of the blast furnace during the feeding of melt, but it is no substitute for exact information concerning the height of the slag layer in the converter at all times during the course of the reaction.